Dryers are already known of the type with a rotating drum that is filled with a regeneratable drying agent, whereby due to the rotation of the drum the drying agent alternately goes through a drying zone in which the drying agent is used to dry compressed gas, and a regeneration zone in which the drying agent is regenerated by bringing it into contact with a hot gas.
Regeneration here means the process by which a drying agent saturated or almost saturated with moisture is stripped of the absorbed or adsorbed moisture by bringing it into contact with a regeneration gas that will remove the moisture from the drying agent. The drying agent will then be able to be used again for drying.
Because the drum rotates, a regenerated drying agent will come into the drying zone and a saturated drying agent into the regeneration zone.
A disadvantage of such a dryer is that the separation between the different zones is not guaranteed and that leaks occur, such that it is possible that regeneration gas leaks to the dried gas.
Dryers of the type with two separate vessels are already known, whereby the vessels are each alternately operated to dry compressed gas and to be regenerated.
By using a suitable system of pipes and valves the two vessels can be switched over.
A disadvantage of such a device is that the slowest process, i.e. in most cases the saturation of the drying agent by drying, will determine the operation and efficiency of the dryer.
An additional disadvantage of both aforementioned known dryers is the fact that fixed volumes are used for the drying and regeneration zones, which cannot be adjusted according to what is required by the situation or circumstances.